<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>test</title>
    <script src="js/jquery.js"></script>
</head>
<body>

<form action="/email" method="post">
    <input type="email" onblur="checkEmailFormat(this)" required>
    <input type="submit" value="提交">
</form>
</body>

<script type="text/javascript">
    function checkEmailFormat(s) {
        var format = /^\w+(\.\w+)*@\w+\.\w+(\.\w+)*$/i;
        return format.test(s);
    }
</script>

</html>